The Wheatstone offshore platform remained partly shut down three days after the first media report that routine maintenance uncovered a problem with a crucial pressure vessel.

The maintenance finding likely sent shockwaves through Chevron Australia’s Perth headquarters that has just seen the end of a five-month shutdown of an LNG train at its Gorgon LNG project after inspectors found faulty welds.

That incident cost about $500 million in lost production, a second Gorgon train is now out of action for inspection, and the third train on Barrow Island will follow.

Reuters reported on Tuesday that an anomaly within a nozzle on an inlet separator vessel was found during routine maintenance on the Wheatstone platform.

The inlet separator receives fluids directly from the subsea wells and separates the flow into gas and liquids.

A Chevron spokesperson yesterday told Boiling Cold that the large pressure vessel remained shut down as a precaution while it undertook additional assessments.

“Inspection of the equivalent nozzle on a similar separator on the platform has confirmed that nozzle is not affected by an anomaly,” the Chevron spokesperson said.

“We are committed to the safety of our workforce and the safe and reliable operation of our facilities.”

The offshore safety regulator NOPSEMA has met with Chevron and is examining the risks associated with Wheatstone, a spokesperson for the regulator told Boiling Cold.

“There is no immediate threat to safety as the areas of concern at the facility have been temporarily shut down,” the NOPSEMA spokesperson said.

“NOPSEMA is assessing information provided by Chevron and has requested additional information.”

The $US34 billion Chevron-operated Wheatstone project can produce 8.9 million tonnes of LNG a year and 200 terajoules of gas a day for the WA market.

The Wheatstone offshore platform receives about 80 per cent of its gas from the Chevron-operated Wheatstone-Iago fields and the remainder from the Woodside-operated Julimar-Brunello fields.

A Woodside spokesperson referred questions about the platform to Chevron that operates the facility.

“If there is any material impact on our production, we will report that to the market as required,” the Woodside spokesperson said.

Chevron said both Wheatstone LNG trains remained operational and deliveries continued to international and WA customers.

The Wheatstone domestic gas plant supplied 16 per cent of the WA gas market in November at an average rate of 165 terajoules a day of gas, according to the WA Gas Bulletin Board. The plant has maintained that rate into December, including this week since the anomaly was reported.

If the partial shutdown of the platform has reduced gas production, Chevron could maintain domestic gas output for a short time with so-called linepack: gas already in the 225km-long pipeline to shore.

A prolonged partial shutdown would likely require a reduction in LNG production for supply to WA to be maintained.

The Wheatstone platform, like the propane heat exchangers that caused problems at Gorgon this year, was built in South Korea.

Wheatstone topsides installation. Source: Chevron

A 36,000-tonne steel gravity structure was towed from South Korea to location and filled with water to set it on the seabed, and was then ballasted with 115,000 tonnes of iron ore.

The 37,000 tonnes topsides built by DSME was installed on the SGS on schedule in 2015. However prolonged and expensive rectification work was then required to fix numerous issues, including faulty valves and piping.


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Main image: Wheatstone platform. Source: Chevron Australia Pty Ltd